The present invention relates generally to operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a well control system utilizing digital hydraulics.
It is very advantageous to be able to independently control well tools from the earth""s surface, or other remote location. For example, production from one of several zones intersected by a well may be halted due to water invasion, while production continues from the other zones. Alternatively, one zone may be in communication with a production tubing string, while the other zones are shut in.
In order to control multiple downhole well tools, various systems have been proposed and used. One type of system utilizes electrical signals to select from among multiple well tools for operation of the selected tool or tools. Another type of system utilizes pressure pulses on hydraulic lines, with the pulses being counted by the individual tools, to select particular tools for operation thereof.
Unfortunately, these systems suffer from fundamental disadvantages. The systems which use electrical communication or power to select or actuate a downhole tool typically have temperature limitations or are prone to conductivity and insulation problems, particularly where integrated circuits are utilized or connectors are exposed to well fluids. The systems which use pressure pulses are typically very complex and, therefore, very expensive and susceptible to failure.
From the foregoing, it can be seen that it would be quite desirable to provide a well control system which does not use electricity or complex pressure pulse counting mechanisms, but which provides a reliable, simple and cost effective means of controlling downhole tools. It is accordingly an object of the present invention to provide such a well control system and associated methods of controlling well tools.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a digital hydraulic well control system is provided which utilizes hydraulic lines to select one or more well tools for operation thereof, and which utilizes hydraulic lines to actuate the selected well tool(s). The use of electricity downhole is not required, nor is use of complex pressure pulse decoding mechanisms required. Instead, the digital hydraulic well control system utilizes a combination of pressure levels on the hydraulic lines to select a well tool for actuation, and uses pressure in one or more hydraulic lines to actuate the tool.
In one aspect of the present invention, a method of hydraulically controlling multiple well tools in a well is provided. A set of hydraulic lines is interconnected to each of the tools. At least one of the tools is selected for actuation thereof by generating a code on the set of hydraulic lines.
The code is a combination of pressure levels on the set of hydraulic lines. For example, one or more of the hydraulic lines may have a certain pressure level, while other hydraulic lines have another pressure level. Pressure pulses are not used.
The code corresponds to an address of one or more actuation control devices. For example, each well tool may have an actuation control device associated therewith. When a certain code is transmitted by the hydraulic lines, and the code matches the address of one or more of the actuation control devices, the corresponding tool(s) are selected for actuation thereof.
When a well tool has been selected for actuation, fluid pressure in one or more of the hydraulic lines may be used to operate the well tool. The hydraulic line used to operate the tool may be one of the hydraulic lines also used to select the tool for actuation, or it may be another hydraulic line. If the hydraulic line used to operate the tool is one of the hydraulic lines used to select the tool for actuation, a change in fluid pressure in that line may be all that is needed to cause the tool to actuate.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings.